When starting an aircraft engine in very cold weather, a check valve or thermally activated valve is needed in the oil system to address the problem of extreme oil viscosity in low temperatures. These valves typically provide an oil bypass so that the oil is not delivered to the engine until the oil begins to warm and the engine oil system can function in its normal operating temperature range. A gas turbine engine usually has enough residual oil on its moving parts to allow it to start without needing additional oil at start-up. However, check valves or thermally activated valves are prone to failure, which can be detrimental to aircraft engine lifespan and reliability if either cold, highly viscous oil is allowed to flow at start-up or if no oil reaches the engine after the engine has been started.
There is thus a need for a flow control device that is generally more reliable and not prone to failure.